Revenge: Casey McDonald Style
by CrazyNerdyFangirl
Summary: Casey's model cousin Lauren visits and decides to set her sights on the lovely Derek Venturi. Things get messy when Lauren decides she has to meet Casey's boyfriend, who's probably some boring sod anyway - he's dating CASEY, of all people. Touch of Derek/OC but mostly Dasey. One-shot.


**AN: I don't know if this fandom is dead or not, but I recently rediscovered LWD, realized this fandom was a thing, and had too many feelings not to write fic. Enjoy!**

The house intact? Check. Silk sheets on a perfectly-made bed? Check. Lauren's list of required lotions and bathroom commodities perfectly lined up next to the sink? Check. No chance that Lauren will run into Casey's stepbrother? Well –

"Der-_ek_," Casey shrieks, attempting to shoo him off the bed. "Lauren's going to be here in an hour, so you need to get out, out, out right now before she sees you." Their fights have always strayed toward the more physical side, and Casey doesn't actually know when she managed to grab hold of a frying pan, but it's a useful weapon, so she isn't complaining. Derek's sort of screaming, but _good_, she hopes she leaves bruises. The jerk deserves it for existing.

"Ow, you crazy woman, what the _hell_?" Derek brings up his hands to cover his face.

"You're only hanging around because you want to hook up with her. Well, let me tell you this. Nope, no sir, not going to happen. Because I have a foolproof plan to keep you out of Lauren's pants, and it's going to work," Casey hisses. "I'd rather not be greeted by you and Lauren's tongues down each other's throats every morning, thank you very much. I like eating, and breakfast is the most important meal of the day."

Derek's hand clutches his chest in a caricature of a wounded heart (as if Derek had a heart to be wounded in the first place). "You have so much faith in me." When Casey's expression refuses to lighten up, he sighs and pats her knee reassuringly. "I promise I won't try to sleep with your cousin. Even though that picture of her you showed me promised me some very nice legs."

"Whose legs are we talking about?" comes a voice from the doorway. "Oh my God, is that you, Casey?" Skinny arms encircle Casey's waist, and damn, this girl has a grip. She can hear Derek's muffled laughter, but she's ignoring him, yes, she is, because she already knows how ridiculous she looks next to her gorgeous cousin – she doesn't need him to rub it in her face. "You look so _grown-up _now. And that dress, so adorable. I didn't know we were dressing like ten-year-olds – what a great idea. If you'd told me, we could have matched!"

"Hi, Lauren," Casey manages to squeeze from between her reluctant lips.

With an exaggerated gasp, Lauren whirls around and spies Derek, who's still leaning against the headboard without a care in the world. "And _you_must be Derek." She nudges Casey with all the subtlety of a rampaging bull. "Casey, you didn't tell me he was going to be home." A slow grin slowly creeps up Lauren's face. "Hi, Derek, I don't think we've met. I'm Lauren, Casey's cousin?"

Derek accepts her hand and shakes it. "Nice to meet you too."

Casey may have been able to let it go if he hadn't been blatantly staring at her boobs the entire time. And her legs. And her flippy hair. And just her in general, really. That was her stepbrother, always the charmer.

Too bad Lauren doesn't seem to mind very much.

* * *

"So, Casey, when are we meeting this new boyfriend of yours?" Lauren asks at the dinner table. Everyone's been caught up with the whole story. Lauren and Casey haven't seen each other in ten years. Lauren decided to catch up with her cousins. Lauren is in town anyway for some modeling thing. Lauren is totally and completely welcome for the two weeks she's in London because that's what family's for – free stuff.

Lauren, Lauren, Lauren.

"He's not my new boyfriend," Casey manages to grit out between her teeth, "I've been dating him for two years, actually."

"So what is he – computer engineer? Life-saving doctor? Physics professor?"

"Professional geek, you mean?" Derek stabs a meatball with glee, thoroughly loving the dinner conversation. "Yeah, I've met the guy. He really, really is someone worthy of Casey's keener…ness." He elbows Casey. "Isn't that right, sister dearest?"

Edwin snorts into his food, and Lizzie suddenly finds that it's impossible to eat her spaghetti without splitting it up into four neat sections on her plate. Marti opens her mouth to speak, but George slaps a hand over her mouth before she can utter a word.

"Of course, brother dear." If feigning nice were an Olympic sport, Casey should get a medal.

"Casey, if you ever, ever get tired of just dating nerds, I could totally help. I just broke up with my boyfriend – he was a model too – and I'd be happy to hook you up with one of my other model friends, provided that you fix your hair, and change your clothes, and probably get that overbite fixed. Oh, I know, I could be your makeover consultant. Anything you need, Case, don't you worry about a thing. I'll be happy to help, really. Knock your nerdy boyfriend off his feet, am I right?" Lauren places a hand on over Casey's and _goddamn_, she's never believed in cooties before, but she kind of does now. Tact, meet Lauren. Wait, Tact, you don't _want _to get acquainted with Lauren? No, Tact, come back and shove yourself into this girl's mouth before she says anything worse, you sneaky motherfucker.

"I'm sure Casey, um, appreciates your offer of help, but I really think she has the boyfriend situation under control, Lauren," Nora says. Across the table, Casey mouths a silent "thank you."

"Nonsense!" Lauren waves a hand in dismissal. "We're all family here, and I'm _sure_Casey wouldn't want to settle. God, a McDonald should never have to settle, right?"

Casey shoves her chair back. "You know what – "

"Casey! Isn't there that new show you wanted to watch – that thing like –yeah?" Grabbing on to Casey's sleeve, Lizzie attempts to pull her back down. Casey vaguely hears Derek mutter something about a catfight and rabid bulldogs, and he seems way too happy for someone who's getting his ass kicked later (and that's going on her schedule, no negotiations).

"Lizzie, let me go," Casey says coldly.

Lauren turns the full force of her big blue eyes on her cousin. "Something wrong, Casey?" she says sweetly.

Before Casey can reply that _yes,_ something's definitely wrong and _yes_ that thing is sitting right in front of her and _please _can we just kick Lauren to the curb already, Nora answers, "No, nothing's wrong with Casey. In fact, she needs to go to bed early."

Okay, Lauren may have won this round, but Casey's determined to win the war.

* * *

"So why's Lauren so bad again?"

It's the first time she's actually managed to get Derek away from Lauren for days – Lauren's at some spa getting "the beautification she needs and it's too bad you can't come too, Casey" – and true to typical McDonald-Venturi fashion, they're dealing with the multitude of problems that plague this family. When Marti mentioned a "ritual burning of her stuffed animals," Casey had never imagined that she and Derek would be the ones setting up the funeral pyre.

"Well, in first grade, she visited from France for the first time? I didn't have any friends because, well, the kids didn't appreciate the perfectly organized study schedules I wrote out for all of them." Casey points an accusing finger at Derek. "_Don't you dare start laughing._" When he finally manages to calm down, she turns back to gutting Marti's old stuffed cow and says with practiced airiness, "Let's just say I had even less friends when she was through with me. And then in seventh grade, she visited again and told Timmy Michaels that I had a crush on him. She then proceeded to flirt with him and, like, every other seventh grade boy. He saw her legs and the…assets and decided nope, Casey McDonald just wasn't good enough. And then in eighth grade, she actually stayed the whole year and decided that she was going to steal the student council presidency away from me. She almost did too, if I hadn't found that picture of her rolling around in a cow pie. And then – "

"_You _campaigned dirty?" Derek asks in disbelief as he pokes the eyes out of a robot's head.

Casey huffs. "Don't blame me. Blame Lauren. She's the one who drives me to do all the crazy stuff."

It's strange, but Casey can't help thinking their roles are reversed. Here she is, planning to get her cousin's head on a pike, and Derek's being _sensible _and _calm_? God, it's like pigs are flying or something (in fact, Casey should really check the skies). She hadn't wanted Lauren to come, of course not. But one not-so-adamant _no_ led to one thing and that one thing led to another and _that_one thing led to Lauren ruining a perfectly good two weeks of summer vacation.

"Maybe it's time you could…let it go?"

"No! I mean, she's always rubbed everything in my face. The fact that she's a model. Her money. Her boyfriends. It's time I win at something."

Maybe the declaration would have been more emphatic if Casey hadn't been holding a pink stuffed caterpillar in her hand. Goddammit, googly eyes keep ruining things.

"It's time I win at something," Derek mimics. "Don't you think you sound a little bit, I don't know, ten?"

"Will thinking like a ten-year-old help me win the war? Because if it does, I'll embrace my inner ten-year-old." As if to emphasize the point, she hugs the Barbie she's holding to her chest.

"Yeah, I don't think ten-year-olds play with Barbies. Casey, Casey, Casey." Before she can get away from him, his hands are on her shoulders in a sad attempt at comfort – though knowing Derek, it's probably more like patronization. Or an excuse to spread his germs onto her. "When will you learn that you suck at the whole revenge thing?"

Casey decides to ignore him – an ability she's actually getting pretty good at. Kind of. "And _why _didn't you defend my boyfriend? You know he's probably as far from 'professional geek' as you can get – short of becoming one of those homeless people who live under highways."

"Maybe it's because I think he can defend himself, you know, when he visits," Derek says pointedly.

"He'll visit when he visits, Derek. I'm not giving you more of a chance to antagonize him."

"Oh, I think he gets enough antagonizing from you – " Casey throws a stuffed dinosaur at him out of habit. "What's this…green stuff on it?" Derek pinches the dinosaur's tail between two fingers and holds it away at arm's length. Casey bursts into laughter at the look on Derek's face. He gags, "Remind me why we have to do this again?"

"Marti's a big fan of metaphor now."

"But does she have to burn stuffed animals to get Dad to stop treating her like a kid? Why can't she just _talk _to him?"

"She's fourteen, Derek. She's allowed to be a little…" Casey nudges the remaining stack of toys with her boot, "…rebellious."

Casey hears a rush of feet on the grass and turns to see Marti, cheeks flushed and panting. "Okay, Dad's here. We can start the ritual burning now." Marti's holding a lighter in one hand and a can of gasoline in the other, and Casey can't help but wonder when this family's getting the therapy it so obviously needs. "Smerek, hurry the hell up." Marti shoves the lighter into Derek's hands and pushes him toward the pile of desecrated toys with all the force a fourteen-year-old can muster. "Go, go, go," she urges, glancing over her shoulder to make sure George hasn't caught up.

"It's _your _ritual burning," complains Derek, "why can't you burn them yourself?" But he's already opening the can of gasoline and pouring it out as quickly as he can because even after all of these years, they're still Smarti and Smerek.

"I'm afraid of fire, duh," Marty replies matter-of-factly. "Hurry!"

Later, when George is weeping over the metaphorical loss of his youngest daughter, Marti looks like she'd be high-fiving herself if she could, and the flames are blazing to an unfortunate (or fortunately if you were Marti) height, a shriek resounds around the house. "Oh my God! Someone get water and a hose, oh my God! There's a fire in the backyard."

Marti gives Lauren the most adorable smile she can afford to give, considering the fact that she's now a responsible, independent young adult who's eschewing all forms of coddling. "Oh, don't worry. It's completely under control."

"But – " Lauren sputters, " – what if the house catches on fire, and I die?"

Edwin mutters something that sounds like "all the better for us," which Lauren proceeds to ignore.

Casey snaps her fingers in sudden realization. Turning to Derek, she whispers, "I _thought _this fire was missing something. Don't you think Lauren would look fantastic on top of it?"

* * *

It's kind of awkward being at a club with Lauren, Derek, and Emily, but Casey's trying to make the best of it. Lauren's constant babbling at her ear doesn't really make things better, but she's trying. She's really, really trying. So far, Lauren's theory that alcohol makes everything more fun is resisting truth.

"Your brother's so cute – you never told me how cute he was. Derek's a burgeoning _director. _Isn't that fantastic? We're both artists," Lauren practically screams over the music.

"Stepbrother." Casey's response is automatic. "…And you're an artist?" she says, amused.

"Hello?" She gestures at herself. "I'm a _model_. We make art with our bodies."

Casey wonders if Lauren knows how ridiculous she sounds or if she's just playing it up for the unfortunate benefit of everyone else.

Emily seems to sense the tension in the room. "So – Lauren, how's the modeling thing?"

Lauren brightens immediately. Because of course, Lauren's favorite thing is Lauren. "Oh, so _grand_. The guys. Think of the guys. I already offered to introduce Casey to some."

"But Casey has a boyfriend," Emily says cautiously, as if she's missing something.

"Ha, Derek said that he was lame, and does Casey really want to put up with _boring_for the rest of her life?"

Emily looks at Casey suspiciously. "Casey's dating – "

Swift kick to Emily's shin under the table? Not very sophisticated but perfectly effective. "We're not here to talk about Casey's love life," Casey hints. She raises her eyebrows, hoping that her (very subtle) eyebrow-raising is enough to convey messages.

"I mean, I'm not surprised." Lauren says to Emily conspiratorially, "I mean, Casey's such a dork that it's no wonder she got stuck with one." At Casey's insulted expression she dismisses, "Oh, don't look at me like that, Casey. You know I'm right."

"Who's always right?" Derek slides into the seat next to Lauren, drink in hand and smelling of alcohol. He didn't even have the decency to get Casey anything – God knows alcohol is the only way to get her through this night of hell.

"What? No blonde bimbo hanging off your arm?" Casey says scathingly.

"Whoa, someone's definitely not in a good mood." Turning to Lauren, Derek says, "You'll have to excuse my stepsister. She's kind of…spacey."

"Don't worry – I mean, at least you're not related to her by blood." Switching her attention to Casey, she chastises, "You're so boring, Casey. I mean, look at guys like…guys like Derek!" Lauren gestures to him, and Casey wants to wipe that smug look off his face.

"Guys like me?"

"Yeah. Fun, good-looking guys don't go for the boring type." Lauren takes another swig of her drink and accidentally spills some of it on her chest. Wiping it off in what she probably figures is a seductive manner, she bats her fake eyelashes at Derek.

"The Casey type?" he asks, amused.

"Exactly! I mean, you get it, Derek." When Lauren finally notices the white-knuckled grip Casey still has on her glass, she pats her shoulder awkwardly. "Oh, honey, I'm just trying to help you. Don't give me that little puppy look." Before Casey can protest that unless she looks like a _murderous _little puppy, Lauren should probably get her eyes checked, Lauren ploughs on, "You understand, right?"

Meanwhile, Emily's staring at the entire exchange with wide eyes. Casey almost feels sorry for her, but it's all a part of the Master Plan, and she can't deviate from the plan (nope, not Casey McDonald). Finally, Emily raises a trembling hand and says, "Wait, I don't think _I_understand what's going on." Her eyes flicker from Derek to Casey and back again, confused. "You two are – "

Another kick under the table.

"What was that for, Spacey?" Derek yelps.

Oops.

* * *

"Let's examine the facts." Edwin hauls a whiteboard on top of the dining room table and wields a pack of multicolored markers. "Here's a chart of Lauren's presence in this house, number of hours on the y-axis, day of visit on the x." He rummages through his supplies for a few minutes, only to finally give up and yell, "I said pink, Lizzie! I told you pink."

"Edwin, there're twenty-five markers in that pack. Surely, there's a pink one in there somewhere," retorts Lizzie.

"Well, there isn't. And we needed pink to prove our point."

"Stop being a baby!"

"I'm not being a baby. I'm being scientifically correct. _There's a difference_."

Nora finds herself rubbing her temples, tired. "You called a family meeting to discuss the integrity of using pink markers to demonstrate your point?"

Edwin clears his throat. "Anyway," he points toward the graph dramatically," as you can see, the number of hours she's spent in this house has been increasing exponentially. And the reason for that is simple…and also poking me – _Derek, you're an adult, stop acting like a child._"

Casey pulls Derek back onto the couch, and for once, he actually complies – probably because she shoves a chocolate-chip pancake into his mouth. For, of course, the way to Derek's heart is through his stomach.

"This," Edwin points to the graph next to it, "is a graph of my happy level. As you can see, _I'm not happy_."

"You made a scale to judge your happiness?" Derek asks. He examines the footnote at the bottom of the graph. "Smiling 90% of the day equals a ten? Derek not showing up equals an eight? Wow, I'm flattered. I have my own level." He pats Edwin on the back absently. "I never knew my presence was so traumatic. I'm better than I thought."

Edwin crosses his arms over his chest defiantly and decides to ignore his brother. "My happiness is inversely proportional to the time Lauren spends in this house. She's annoying, and she doesn't like me, and she won't let me watch my cartoons in peace – "

"She told me girls shouldn't be so sporty," Lizzie's quick to add.

"And she _smells_ like _springtime_." Marti makes a face.

"Lauren's continuing presence leaves me…" Edwin rips the graphs off the board with a flourish and grabs the first marker he can reach. "The hell? I said pink – " Lizzie shoves a red marker into his hand, and he sighs in defeat. "Is nothing sacred anymore?" he mutters to himself. Edwin begins drawing what is possibly the ugliest frowny-face to grace the smooth, previously unmarred surface of the whiteboard. "…It leaves me looking like this." When Edwin sees that none of his family members have begun leaping off the couch to praise his artistic abilities, he reluctantly clarifies, "For the record, the face is frowning. Which means I'm sad. Which is bad. Because everyone should want me to be happy."

George turns to Nora. "Since Marti's growing up, do you think Edwin's reverting to his inner child as a defense mechanism for leaving the nest?" he asks seriously.

"Oh, I hope not. One childhood with Edwin was enough – "

"All of you are completely missing the point!" Edwin yells. "I think I'll take my _science_somewhere else." Grabbing his whiteboard and graphs, he marches away in a huff. On his way out, he wrenches the pancake from Derek's hands and shoves it into his own mouth. "Take that, you pathetic excuse for a brother."

"Hey, that was mine!" Derek rises out of his seat to avenge the loss of his pancake, but Casey's grip on his arm's stronger than he thought it was.

"And to think, Edwin's going to be a biochem major. I thought that was for smart people," says Marti, shaking her head.

Lizzie speaks up, kind of awkwardly. "You know, I think the conclusion to this was supposed to be that Derek has to figure out a way to keep her away from us."

Derek throws his hands to the skies. "Why _me_?"

"Because she wants to get in your pants," Marti says simply. To George, she says gently, "Dad, that shade of red looks horrible on your face. Have you considered water massage? It's supposed to help with the stress."

Casey can hear the sound of the front door unlocking, and everyone attempts to force themselves to look normal again – or as normal as this family will ever be. George's angry red face is taking a while to calm down, and maybe Marti's right. Casey should really start looking into masseuses.

Lauren enters the room with a flourish. "I'm _back_, everyone!" she sings. "Did you miss me?"

* * *

Sitting for a prolonged amount of time in Lauren's presence isn't exactly on Casey's top ten things she wants to do (in fact, bottom ten would probably be more accurate). Sitting in a booth at Smelly Nelly's waiting for Derek and her boyfriend to show up so that they can have a proper double date ranks even lower on the list, barely above listening to Edwin make fart jokes for an hour (which he actually did yesterday – maybe George is right and the kid really does have issues with growing up).

Needless to say, Casey's foolproof plan to keep Derek away from Lauren didn't work out. (She does have to admit that castration was a little bit too far-fetched, even for her.) As soon as Lauren rubbed her chest on Derek's arm and blinked those big blue eyes, the "yes" to a date had been inevitable.

"And we could use this date to get to know your boyfriend too, Casey! It's like killing two fish with one stone," Lauren insists. Yeah, Casey really wants to kill those two fish, alright. More likely Lauren wants to rub in the fact that _her_date is successfully not-boring, leaving Casey to question her boyfriend's merits.

"I really can't wait to meet him," Lauren says sweetly.

"And I'm sure he's looking forward to meeting you."

If his feelings are anything like the breadstick Casey's currently ripping in two, it's pretty fair to say that meeting Lauren's probably at the bottom of his I-really-want-to-do-this list too.

Lauren glances at her watch. "Derek's late – do you think anything happened to him?"

"Knowing Derek, I'd be more worried if he were actually on time."

Biting her lip, Lauren gives her watch another glance. "Maybe I should call – "

"No need. D-Vent is _here_." Derek barrels into their booth and nearly knocks Casey over as he sits next to her. He slings an arm around her shoulders and pats her head. "How's my favorite stepsister and her," he winks at Lauren, "lovely cousin?"

Casey buries her face in her hands. "Please not the D-Vent thing."

"See, Casey? Derek's responsible, unlike that boy of yours. You should really teach him some manners, Case – "

"Actually, I just came to tell you I have to cancel this date thing," Derek interrupts.

"But – but you're already here! Why would you _come _just to _cancel_?" Lauren's face slowly begins to turn a lovely shade of red, and Casey can't help but think that this ill-fated double-date just got about a hundred times more interesting.

"I'm cancelling my date with you." Derek smiles. "But I still have a date with my girlfriend."

It takes a full minute for the revelation to sink it.

Her face devoid of color, Lauren's gaze fixes on the arm Derek has around Casey. Eyes travel from Casey's smirking face to Derek's unaffected expression and back again. Her breathing goes shallow, and it takes every effort to suck in enough air to finally get her lungs working again.

And boy did they work.

"But you – and Casey – gah! It's like incest! With stepsiblings! Stepcest!" Lauren accuses, pointing her finger wildly.

Edwin leaps out from behind the counter, nearly knocking over a waitress in the process. "Surprise!"

Lizzie and Marti reveal themselves too. "Sorry, Casey. We just really wanted to see the look on Lauren's face," Lizzie explains.

"Yeah, I was hoping she'd throw something," Marti says hopefully.

"You know, when it comes to Casey and Derek, Lauren, I think incest is wincest," says Edwin. When Casey throws a breadstick at him (for good reason), he raises his arms in surrender. "What? I like puns, okay?"

"But – " Lauren stamps her foot in a perfect imitation of six-year-old Marti. "Casey's boring and bland and this wasn't supposed to happen. You – " She grabs Derek's collar and pulls his face toward hers. "You _said_she was dating some loser geek," hisses Lauren. A manic glint alights in her eyes, and wow, if Casey looks like that when she's mad, no wonder everyone thinks she's completely off her rocker.

"Well, I did _kind_of try in college." Lauren twists his collar. "Hey, it counts! Does violence run in this family?"

Lauren lets Derek go with a shove, and he rubs his neck in relief. It's Casey's turn to get yelled at. "You're so – so – Casey! I mean, you don't even know how to have sex!"

"That's very debatable," says Marti. At Casey's inquiring look, she admits, "Well, see, you and Derek are very…loud."

"It's very disturbing," adds Lizzie.

"It scares me," whispers Edwin. "Hey, did you save any of Marti's old toys from that fire? Because I really don't think this growing up thing is working out so well for me – "

Lauren decides that this is the right time to start ignoring them. "_Why_ would you settle for Space Case over here when you could have a model? When you could have _me_?"

Noting the crazed expression in her eyes and the startlingly strong grip she has on her fork, Derek says, "Yeah, I think I'm going to have to go with the lesser of two evils." He pulls Casey closer.

And then the final touch comes, the perfect ending to a truly horrific visit.

When Derek kisses her, Casey can almost forgive him for that less-of-two-evils comment. She can hear Lauren's continued puffs of anger, Edwin's gagging sounds, and Marti's snort, but what finally breaks the haze caused by Derek's kiss is –

"I knew I wasn't going crazy!" cries Emily. "You two are still going at it like two rabbits in heat!" She shakes her head and gazes at them, half-amused, half-disgusted. "And here I thought I was getting punked or something."

* * *

"So…thank you for playing along," Casey says when she and Derek finally have the house to themselves. Luckily, Lauren's visit inflicted no lasting damage to the household – about a day after her leave, everything's just about back to normal. More importantly, Casey and Derek are back to normal. Her head is tucked under his chin, and his arms are wrapped around her as they watch a hockey game (his choice – she figures he deserves _something_for playing along). "I know it was weird of me to ask you to do that – "

"You know how much I love a good prank. And besides, it was kind of fun to see the look on her face."

Casey chuckles. "Yeah, she looked like she was about to flay chickens alive."

Suddenly, something seems to strike Derek. "Do you remember what Lauren said earlier? About you not knowing how to have sex?"

"Are you _feeding me a line_?" Casey hits Derek with a couch cushion. "We've been dating for two years. I'm pretty sure you can do away without cheesy pick-up lines now."

"Well, maybe I want to change things up a little," he defends. Casey grins and knocks him over, hooking her leg – "Stop pushing me, woman! Wait, no, I like this position – no, don't slap me – yeah – no – hell, remind me why I put up with you – "


End file.
